Hydrofluorocarbon compositions

ABSTRACT

Refrigerant compositions include mixtures of difluoromethane and isobutane, butane, propylene or cyclopropane; pentafluoroethane and propylene or cyclopropane; 1,1,2,2-tetrafluoroethane and propane; 1,1,1,2-tetrafluoroethane and cyclopropane; 1,1,1-trifluoroethane and DME or propylene; 1,1-difluoroethane and propane, isobutane, butane or cyclopropane; fluoroethane and propane or cyclopropane; 1,1,1,2,2,3,3-heptafluoropropane and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane and butane, cyclopropane, isobutane or propane.

This is a division of application Ser. No. 08/208,777, filed Mar. 11, 1994, now U.S. Pat. No. 5,417,871.

FIELD OF THE INVENTION

This invention relates to refrigerant compositions that include a hydrofluorocarbon as a component. These compositions are also useful as cleaning agents, expansion agents for polyolefins and polyurethanes, aerosol propellants, refrigerants, heat transfer media, gaseous dielectrics, fire extinguishing agents, power cycle working fluids, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, and displacement drying agents.

BACKGROUND OF THE INVENTION

Fluorinated hydrocarbons have many uses, one of which is as a refrigerant. Such refrigerants include dichlorodifluoromethane (CFC-12) and chlorodifluoromethyl (HCFC-22).

In recent years it has been pointed out that certain kinds of fluorinated hydrocarbon refrigerants released into the atmosphere may adversely affect the stratospheric ozone layer. Although this proposition has not yet been completely established, there is a movement toward the control of the use and the production of certain chlorofluorocarbons (CFCs) and hydrocholrofluorocarbons (HCFCs) under an international agreement.

Accordingly, there is a demand for the development of refrigerants that have a lower ozone depletion potential than existing refrigerants while still achieving an acceptable performance in refrigeration applications. Hydrofluorocarbons (HFCs) have been suggested as replacements for CFCs and HCFCs since HFCs have no chlorine and therefore have zero ozone depletion potential.

In refrigeration applications, a refrigerant is often lost during operation through leaks in shaft seals, hose connections, soldered joints and broken lines. In addition, the refrigerant may be released to the atmosphere during maintenance procedures on refrigeration equipment. If the refrigerant is not a pure component or an azeotropic or azeotrope-like composition, the refrigerant composition may change when leaked or discharged to the atmosphere from the refrigeration equipment, which may cause the refrigerant to become flammable or to have poor refrigeration performance.

Accordingly, it is desirable to use as a refrigerant a single fluorinated hydrocarbon or an azeotropic or azeotrope-like composition that includes at least one fluorinated hydrocarbon.

Mixtures that include a fluorinated hydrocarbon may also be used as a cleaning agent or solvent to clean, for example, electronic circuit boards. It is desirable that the cleaning agents be azeotropic or azeotrope-like because in vapor degreasing operations the cleaning agent is generally redistilled and reused for final rinse cleaning.

Azeotropic or azeotrope-like compositions that include a fluorinated hydrocarbon are also useful as blowing agents in the manufacture of closed-cell polyurethane, phenolic and thermoplastic foams, as propellants in aerosols, as heat transfer media, gaseous dielectrics, fire extinguishing agents, power cycle working fluids such as for heat pumps, inert media for polymerization reactions, fluids for removing particulates from metal surfaces, as carrier fluids that may be used, for example, to place a fine film of lubricant on metal parts, as buffing abrasive agents to remove buffing abrasive compounds from polished surfaces such as metal, as displacement drying agents for removing water, such as from jewelry or metal parts, as resist developers in conventional circuit manufacturing techniques including chlorine-type developing agents, or as strippers for photoresists when used with, for example, a chlorohydrocarbon such as 1,1,1-trichloroethane or trichloroethylene.

SUMMARY OF THE INVENTION

The present invention relates to the discovery of refrigerant compositions of difluoromethane (HFC-32) and isobutane, butane, propylene or cyclopropane; pentafluoroethane (HFC-125) and propylene or cyclopropane; 1,1,2,2-tetrafluoroethane (HFC-134) and propane; 1,1,1,2-tetrafluoroethane (HFC-134a) and cyclopropane; 1,1,1-trifluoroethane (HFC-143a) and dimethyl ether (DME) or propylene; 1,1-difluoroethane (HFC-152a) and propane, isobutane, butane or cyclopropane; fluoroethane (HFC-161) and propane or cyclopropane; 1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca) and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and butane, cyclopropane, isobutane or propane. These compositions are also useful as cleaning agents, expansion agents for polyolefins and polyurethanes, aerosol propellants, heat transfer media, gaseous dielectrics, fire extinguishing agents, power cycle working fluids, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, and displacement drying agents.

Further, the invention relates to the discovery of binary azeotropic or azeotrope-like compositions comprising effective amounts of difluoromethane (HFC-32) and isobutane, butane, propylene or cyclopropane; pentafluoroethane (HFC-125) and propylene or cyclopropane; 1,1,2,2-tetrafluoroethane (HFC-134) and propane; 1,1,1,2-tetrafluoroethane (HFC-134a) and cyclopropane; 1,1,1-trifluoroethane (HFC-143a) and propylene; 1,1-difluoroethane (HFC-152a) and propane, isobutane, butane and cyclopropane; fluoroethane (HFC-161) and propane or cyclopropane; 1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca) and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and butane, cyclopropane, isobutane or propane to form an azeotropic or azeotrope-like composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the vapor pressure of liquid mixtures of HFC-32 and isobutane at 25° C.;

FIG. 2 is a graph of the vapor pressure of liquid mixtures of HFC-32 and butane at 25° C.;

FIG. 3 is a graph of the vapor pressure of liquid mixtures of HFC-32 and propylene at 25° C.;

FIG. 4 is a graph of the vapor pressure of liquid mixtures of HFC-32 and cyclopropane at 0° C.;

FIG. 5 is a graph of the vapor pressure of liquid mixtures of HFC-125 and propylene at 25° C.;

FIG. 6 is a graph of the vapor pressure of liquid mixtures of HFC-125 and cyclopropane at 0° C.;

FIG. 7 is a graph of the vapor pressure of liquid mixtures of HFC-134 and propane at 15° C.;

FIG. 8 is a graph of the vapor pressure of liquid mixtures of HFC-134a and cyclopropane at 0.01° C.;

FIG. 9 is a graph of the vapor pressure of liquid mixtures of HFC-143a and propylene at 25° C.;

FIG. 10 is a graph of the vapor pressure of liquid mixtures of HFC-152a and propane at 25° C.;

FIG. 11 is a graph of the vapor pressure of liquid mixtures of HFC-152a and isobutane at 25° C.;

FIG. 12 is a graph of the vapor pressure of liquid mixtures of HFC-152a and butane at 25° C.

FIG. 13 is a graph of the vapor pressure of liquid mixtures of HFC-152a and cyclopropane at 25° C.;

FIG. 14 is a graph of the vapor pressure of liquid mixtures of HFC-161 and propane at 25° C.;

FIG. 15 is a graph of the vapor pressure of liquid mixtures of HFC-161 and cyclopropane at 25° C.;

FIG. 16 is a graph of the vapor pressure of liquid mixtures of HFC-227ca and butane at 25° C.;

FIG. 17 is a graph of the vapor pressure of liquid mixtures of HFC-227ca and cyclopropane at 25° C.;

FIG. 18 is a graph of the vapor pressure of liquid mixtures of HFC-227ca and DME at 25° C.;

FIG. 19 is a graph of the vapor pressure of liquid mixtures of HFC-227ca and isobutane at 25° C.;

FIG. 20 is a graph of the vapor pressure of liquid mixtures of HFC-227ca and propane at 25° C.;

FIG. 21 is a graph of the vapor pressure of liquid mixtures of HFC-227ea and butane at 25° C.;

FIG. 22 is a graph of the vapor pressure of liquid mixtures of HFC-227ea and cyclopropane at 25° C.;

FIG. 23 is a graph of the vapor pressure of liquid mixtures of HFC-227ea and isobutane at 25° C.; and

FIG. 24 is a graph of the vapor pressure of liquid mixtures of HFC-227ea and propane at 25° C.

DETAILED DESCRIPTION

The present invention relates to compositions of difluoromethane (HFC-32) and isobutane, butane, propylene or cyclopropane; pentafluoroethane (HFC-125) and propylene and cyclopropane; 1,1,2,2-tetrafluoroethane (HFC-134) and propane; 1,1,1,2-tetrafluoroethane (HFC-134a) and cyclopropane; 1,1,1-trifluoroethane (HFC-143a) and dimethyl ether (DME) or propylene; 1,1-difluoroethane (HFC-152a) and propane, isobutane, butane and cyclopropane; fluoroethane (HFC-161 ) and propane or cyclopropane; 1,1,1,2,2,3,3 -heptafluoropropane (HFC-227ca) and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and butane, cyclopropane, isobutane or propane.

The present invention also relates to the discovery of azeotropic or azeotrope-like compositions of effective mounts of difluoromethane (HFC-32) and isobutane, butane, propylene or cyclopropane; pentafluoroethane (HFC-125) and propylene or cyclopropane; 1,1,2,2-tetrafluoroethane (HFC-134) and propane; 1,1,1,2-tetrafluoroethane (HFC-134a) and cyclopropane; 1,1,1-trifluoroethane (HFC-143a) propylene; 1,1-difluoroethane (HFC-152a and propane, isobutane, butane and cyclopropane; fluoroethane (HFC-161) and propane or cyclopropane; 1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca) and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and butane, cyclopropane, isobutane or propane to form an azeotropic or azeotrope-like composition.

By "azeotropic" composition is meant a constant boiling liquid admixture of two or more substances that behaves as a single substance. One way to characterize an azeotropic composition is that the vapor produced by partial evaporation or distillation of the liquid has the same composition as the liquid from which it was evaporated or distilled, that is, the admixture distills/refluxes without compositional change. Constant boiling compositions are characterized as azeotropic because they exhibit either a maximum or minimum boiling point, as compared with that of the non-azeotropic mixtures of the same components.

By "azeotrope-like" composition is meant a constant boiling, or substantially constant boiling, liquid admixture of two or more substances that behaves as a single substance. One way to characterize an azeotrope-like composition is that the vapor produced by partial evaporation or distillation of the liquid has substantially the same composition as the liquid from which it was evaporated or distilled, that is, the admixture distills/refluxes without substantial composition change.

It is recognized in the art that a composition is azeotrope-like if, after 50 weight percent of the composition is removed such as by evaporation or boiling off, the difference in vapor pressure between the original composition and the composition remaining after 50 weight percent of the original composition has been removed is about 10 percent or less, when measured in absolute units. By absolute units, it is meant measurements of pressure and, for example, psia, atmospheres, bars, torr, dynes per square centimeter, millimeters of mercury, inches of water and other equivalent terms well known in the art. If an azeotrope is present, there is no difference in vapor pressure between the original composition and the composition remaining after 50 weight percent of the original composition has been removed.

Therefore, included in this invention are compositions of effective mounts of difluoromethane (HFC-32) and isobutane, butane, propylene or cyclopropane; pentafluoroethane (HFC-125) and propylene or cyclopropane; 1,1,2,2-tetrafluoroethane (HFC-134) and propane; 1,1,1,2-tetrafluoroethane (HFC-134a) and cyclopropane; 1,1,1-trifluoroethane (HFC-143a) and propylene; 1,1-difluoroethane (HFC-152a) and propane, isobutane, butane and cyclopropane; fluoroethane (HFC-161) and propane or cyclopropane; 1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca) and butane, cyclopropane, DME, isobutane or propane; or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and butane, cyclopropane, isobutane or propane such that after 50 weight percent of an original composition is evaporated or boiled off to produce a remaining composition, the difference in the vapor pressure between the original composition and the remaining composition is 10 percent or less.

For compositions that are azeotropic, there is usually some range of compositions around the azeotrope that, for a maximum boiling azeotrope, have boiling points at a particular pressure higher than the pure components of the composition at that pressure and have vapor pressures lower at a particular temperature than the pure components of the composition at that temperature, and that, for a minimum boiling azeotrope, have boiling points at a particular pressure lower than the pure components of the composition at that pressure and have vapor pressures higher at a particular temperature than the pure components of the composition at that temperature. Boiling temperatures and vapor pressures above or below that of the pure components are caused by unexpected intermolecular forces between and among the molecules of the compositions, which can be a combination of repulsive and attractive forces such as van der Waals forces and hydrogen bonding.

The range of compositions that have a maximum or minimum boiling point at a particular pressure, or a maximum or minimum vapor pressure at a particular temperature, may or may not be coextensive with the range of compositions that are substantially constant boiling. In those cases where the range of compositions that have maximum or minimum boiling temperatures at a particular pressure, or maximum or minimum vapor pressures at a particular temperature, are broader than the range of compositions that are substantially constant boiling according to the change in vapor pressure of the composition when 50 weight percent is evaporated, the unexpected intermolecular forces are nonetheless believed important in that the refrigerant compositions having those forces that are not substantially constant boiling may exhibit unexpected increases in the capacity or efficiency versus the components of the refrigerant composition.

The components of the compositions of this invention have the following vapor pressures at 25° C.

    ______________________________________                                         COMPONENTS        PSIA   KPA                                                   ______________________________________                                         HFC-32            246.7  1701                                                  HFC-125           199.1  1373                                                  HFC-134           76.1   525                                                   HFC-134a          98.3   677                                                   HFC-143a          180.6  1245                                                  HFC-152a          85.8   591                                                   HFC-161           130.2  898                                                   HFC-227ca         63.8   440                                                   HFC-227ea         66.6   459                                                   butane            35.2   243                                                   cyclopropane      105.0  724                                                   DME               85.7   591                                                   isobutane         50.5   348                                                   propane           137.8  950                                                   propylene         165.9  1144                                                  ______________________________________                                    

Substantially constant boiling, azeotropic or azeotrope-like compositions of this invention comprise the following (all compositions are measured at 25° C.):

    ______________________________________                                                         WEIGHT RANGES                                                                               PREFERRED                                         COMPONENTS      (wt. %/wt/%) (wt. %/wt. %)                                     ______________________________________                                         HFC-32/isobutane                                                                               61-99/1-39   70-99/1-30                                        HFC-32/butane   65-99/1-35   70-99/1-30                                        HFC-32/propylene                                                                               26-99/1-74   70-99/1-30                                        HFC-32/cyclopropane                                                                            54-99/1-46   54-99/1-46                                        HFC-125/propylene                                                                               1-99/1-99   60-99/1-40                                        HFC-125/cyclopropane                                                                           66-99/1-34   66-99/1-34                                        HFC-134/propane  1-75/25-99  30-75/25-70                                       HFC-134a/cyclopropane                                                                           1-99/1-99   50-99/1-50                                        HFC-143a/propylene                                                                              1-99/1-99   70-99/1-30                                        HFC-152a/propane                                                                                1-78/22-99  30-78/22-70                                       HFC-152a/isobutane                                                                             44-99/1-56   60-99/1-40                                        HFC-152a/butane 54-99/146    70-99/1-30                                        HFC-152a/cyclopropane                                                                           1-99/1-99   20-99/1-80                                        HFC-161/propane  1-99/1-99   20-99/1-80                                        HFC-161/cyclopropane                                                                            1-99/1-99   40-99/1-60                                        HFC-227ca/butane                                                                               61-99/1-39   70-99/1-30                                        HFC-227ca/cyclopropane                                                                         27-82/18-73  40-82/18-60                                       HFC-227ca/DME    1-92/8-99   60-92/8-40                                        HFC-227ca/isobutane                                                                            53-92/8-47   60-92/8-40                                        HFC-227ca/propane                                                                               1-79/21-99  30-79/21-70                                       HFC-227ea/butane                                                                               61-99/1-39   70-99/1-30                                        HFC-227ea/cyclopropane                                                                         24-83/17-76  40-83/17-60                                       HFC-227ea/isobutane                                                                            52-99/1-48   60-99/1-40                                        HFC-227ea/propane                                                                               1-79/21-99  40-79/21-60                                       ______________________________________                                    

For purposes of this invention, "effective amount" is defined as the amount of each component of the inventive compositions which, when combined, results in the formation of an azeotropic or azeotrope-like composition. This definition includes the amounts of each component, which mounts may vary depending on the pressure applied to the composition so long as the azeotropic or azeotrope-like compositions continue to exist at the different pressures, but with possible different boiling points.

Therefore, effective mount includes the mounts, such as may be expressed in weight percentages, of each component of the compositions of the instant invention which form azeotropic or azeotrope-like compositions at temperatures or pressures other than as described herein.

For the purposes of this discussion, azeotropic or constant-boiling is intended to mean also essentially azeotropic or essentially-constant boiling. In other words, included within the meaning of these terms are not only the true azeotropes described above, but also other compositions containing the same components in different proportions, which are true azeotropes at other temperatures and pressures, as well as those equivalent compositions which are part of the same azeotropic system and are azeotrope-like in their properties. As is well recognized in this art, there is a range of compositions which contain the same components as the azeotrope, which will not only exhibit essentially equivalent properties for refrigeration and other applications, but which will also exhibit essentially equivalent properties to the true azeotropic composition in terms of constant boiling characteristics or tendency not to segregate or fractionate on boiling.

It is possible to characterize, in effect, a constant boiling admixture which may appear under many guises, depending upon the conditions chosen, by any of several criteria:

* The composition can be defined as an azeotrope of A, B, C (and D . . . ) since the very term "azeotrope" is at once both definitive and limitative, and requires that effective mounts of A, B, C (and D . . . ) for this unique composition of matter which is a constant boiling composition.

* It is well known by those skilled in the art, that, at different pressures, the composition of a given azeotrope will vary at least to some degree, and changes in pressure will also change, at least to some degree, the boiling point temperature. Thus, an azeotrope of A, B, C (and D . . . ) represents a unique type of relationship but with a variable composition which depends on temperature and/or pressure. Therefore, compositional ranges, rather than fixed compositions, are often used to define azeotropes.

* The composition can be defined as a particular weight percent relationship or mole percent relationship of A, B, C (and D . . . ), while recognizing that such specific values point out only one particular relationship and that in actuality, a series of such relationships, represented by A, B, C (and D . . . ) actually exist for a given azeotrope, varied by the influence of pressure.

* An azeotrope of A, B, C (and D . . . ) can be characterized by defining the compositions as an azeotrope characterized by a boiling point at a given pressure, thus giving identifying characteristics without unduly limiting the scope of the invention by a specific numerical composition, which is limited by and is only as accurate as the analytical equipment available.

The azeotrope or azeotrope-like compositions of the present invention can be prepared by any convenient method including mixing or combining the desired amounts. A preferred method is to weigh the desired component amounts and thereafter combine them in an appropriate container.

Specific examples illustrating the invention are given below. Unless otherwise stated therein, all percentages are by weight. It is to be understood that these examples are merely illustrative and in no way are to be interpreted as limiting the scope of the invention.

EXAMPLE 1 Phase Study

A phase study shows the following composition is azeotropic. The temperature is 25° C.

    ______________________________________                                                                Vapor Press.                                            Composition    Weight Percents                                                                              psia   kPa                                        ______________________________________                                         HFC-32/isobutane                                                                              93.8/6.2      249.6  1721                                       HFC-32/butane  99.0/1.0      246.8  1702                                       HFC-32/propylene                                                                              81.0/19.0     261.5  1803                                       HFC-32/cyclopropane                                                                           85.2/14.8     260.6  1797                                       HFC-125/propylene                                                                             79.5/20.5     229.1  1580                                       HFC-125/cyclopropane                                                                          91.3/8.7      209.6  1445                                       HFC-134/propane                                                                               52.3/47.7     164.3  1132                                       HFC-134a/cyclopropane                                                                         65.5/34.5     137.5   948                                       HFC-143a/propylene                                                                            89.6/10.4     181.2  1249                                       HFC-152a/propane                                                                              45.9/54.1     155.1  1069                                       HFC-152a/isobutane                                                                            75.5/24.5     97.0    669                                       HFC-152a/butane                                                                               85.0/15.0     90.5    624                                       HFC-152a/cyclopropane                                                                         44.3/55.7     117.8   812                                       HFC-161/propane                                                                               44.5/55.5     161.2  1111                                       HFC-161/cyclopropane                                                                          63.4/36.6     140.8   971                                       HFC-227ca/butane                                                                              84.4/15.6     77.5    534                                       HFC-227ca/cyclopropane                                                                        55.8/44.2     126.5   872                                       HFC-227ca/DME  75.6/24.4     101.0   696                                       HFC-227ca/isobutane                                                                           76.8/23.2     90.0    621                                       HFC-227ca/propane                                                                             51.6/48.4     159.8  1102                                       HFC-227ea/butane                                                                              85.8/14.2     76.8    530                                       HFC-227ea/cyclopropane                                                                        55.2/44.8     125.1   863                                       HFC-227ea/isobutane                                                                           77.6/22.4     88.8    612                                       HFC-227ea/propane                                                                             50.4/49.6     157.4  1085                                       ______________________________________                                    

EXAMPLE 2 Impact of Vapor Leakage on Vapor Pressure at 25° C.

A vessel is charged with an initial liquid composition at 25° C. The liquid, and the vapor above the liquid, are allowed to come to equilibrium, and the vapor pressure in the vessel is measured. Vapor is allowed to leak from the vessel, while the temperature is held constant at 25° C., until 50 weight percent of the initial charge is removed, at which time the vapor pressure of the composition remaining in the vessel is measured. The results are summarized below.

    ______________________________________                                                      0 wt %    50 wt %                                                 Refrigerant  evaporated                                                                               evaporated                                                                               0% change in                                  Composition  psia   kPa    psia kPa  vapor pressure                            ______________________________________                                         HFC-32/isobutane                                                               93.8/62      249.6  1721   249.6                                                                               1721 0.0                                       99/1         247.8  1709   247.5                                                                               1706 0.1                                       70/30        240.8  1660   230.3                                                                               1588 4.4                                       60/40        234.8  1619   209.6                                                                               1445 10.7                                      61/39        235.5  1624   212.3                                                                               1464 9.9                                       HFC-32/butane                                                                  99.0/1.0     246.8  1702   246.8                                                                               1702 0.0                                       70/30        232.3  1602   217.4                                                                               1499 6.4                                       65/35        229.1  1580   206.6                                                                               1424 9.8                                       HFC-32/propylene                                                               81.0/19.0    261.5  1803   261.5                                                                               1803 0.0                                       99/1         248.8  1715   248.0                                                                               1710 0.3                                       70/30        259.3  1788   257.7                                                                               1777 0.6                                       60/40        254.3  1753   248.8                                                                               1715 2.2                                       50/50        246.7  1701   235.7                                                                               1625 4.5                                       40/60        236.6  1631   219.6                                                                               1514 7.2                                       30/70        223.8  1543   202.6                                                                               1397 9.5                                       29/71        222.3  1533   200.9                                                                               1385 9.6                                       27/73        219.3  1512   197.6                                                                               1362 9.9                                       26/74        217.8  1502   196.0                                                                               1351 10.0                                      HFC-32/cyclopropane                                                            85.2/14.8    260.6  1797   260.6                                                                               1797 0.0                                       99/1         249.3  1719   248.2                                                                               1711 0.4                                       60/40        250.5  1727   236.5                                                                               1631 5.6                                       54/46        246.0  1696   222.5                                                                               1534 9.6                                       53/47        245.2  1691   219.7                                                                               1515 10.4                                      HFC-125/propylene                                                              79.5/20.5    229.1  1580   229.1                                                                               1580 0.0                                       90/10        224.8  1550   222.4                                                                               1533 1.1                                       99/1         203.9  1406   201.8                                                                               1391 1.0                                       70/30        227.4  1568   225.9                                                                               1558 0.7                                       50/50        217.2  1498   206.5                                                                               1424 4.9                                       40/60        209.9  1447   194.1                                                                               1338 7.5                                       30/70        201.2  1387   183.1                                                                               1262 9.0                                       20/80        191.1  1318   174.8                                                                               1205 8.5                                       10/90        179.3  1236   169.3                                                                               1167 5.6                                       1/99         167.4  1154   166.2                                                                               1146 0.7                                       HFC-125/cyclopropane                                                           91.3/8.7     209.6  1445   209.6                                                                               1445 0.0                                       99/1         202.2  1394   201.3                                                                               1388 0.4                                       66/34        194.9  1344   176.5                                                                               1217 9.4                                       65/35        194.1  1338   174.2                                                                               1201 10.3                                      HFC-134/propane                                                                90/10        140.0  965    83.6 576  40.3                                      75.6/24.4    158.9  1095   143.0                                                                               986  10.0                                      52.3/47.7    164.3  1132   164.3                                                                               1132 0.0                                       25/75        157.3  1085   152.1                                                                               1049 3.3                                       1/99         138.5  955    137.8                                                                               950  0.5                                       HFC-134a/cyclopropane                                                          65.5/34.5    137.5  948    137.5                                                                               948  0.0                                       90/10        126.8  874    116.8                                                                               805  7.9                                       95/5         117.1  807    106.2                                                                               732  9.3                                       99/1         103.2  712    99.5 686  3.6                                       30/70        129.4  892    119.4                                                                               823  7.7                                       15/85        120.2  829    109.5                                                                               755  8.9                                       10/90        115.9  799    107.5                                                                               741  7.2                                       1/99         106.3  733    105.2                                                                               725  1.0                                       HFC-143a/propylene                                                             89.6/10.4    181.2  1249   181.2                                                                               1249 0.0                                       99/1         180.7  1246   180.7                                                                               1246 0.0                                       60/40        178.4  1230   178.1                                                                               1228 0.2                                       40/60        174.7  1205   174.2                                                                               1201 0.3                                       20/80        170.5  1176   170.0                                                                               1172 0.3                                       1/99         166.2  1146   166.1                                                                               1145 0.1                                       HFC-152a/propane                                                               45.9/54.1    155.1  1069   155.1                                                                               1069 0.0                                       60/40        153.7  1060   152.2                                                                               1049 1.0                                       70/30        151.0  1041   146.1                                                                               1007 3.2                                       78/22        147.5  1017   134.5                                                                               927  8.8                                       79/21        147.0  1014   131.9                                                                               909  10.3                                      30/70        153.2  1056   152.0                                                                               1048 0.8                                       20/80        149.9  1034   147.6                                                                               1018 1.5                                       10/90        144.8  998    142.6                                                                               983  1.5                                       1/99         138.6  956    138.2                                                                               953  0.3                                       HFC-152a/isobutane                                                             75.5/24.5    97.0   669    97.0 669  0.0                                       90/10        94.7   653    92.5 638  2.3                                       99/1         87.3   602    86.3 595  1.1                                       60/40        95.7   660    93.9 647  1.9                                       40/60        90.4   623    79.2 546  12.4                                      43/57        91.5   631    82.3 567  10.1                                      44/56        91.8   633    83.3 574  9.3                                       HFC-152a/butane                                                                85.0/15.0    90.5   624    90.5 624  0.0                                       95/5         88.9   613    88.2 608  0.8                                       99/1         86.6   597    86.2 594  0.5                                       70/30        89.0   614    87.4 603  1.8                                       60/40        87.1   601    82.4 568  5.4                                       53/47        85.3   588    76.7 529  10.1                                      54/46        85.6   590    77.6 535  9.3                                       HFC-152a/cyclopropane                                                          44.3/55.7    117.8  812    117.8                                                                               812  0.0                                       70/30        113.8  785    110.9                                                                               765  2.5                                       90/10        100.4  692    94.3 650  6.1                                       99/1         87.6   604    86.5 596  1.3                                       20/80        114.6  790    113.0                                                                               779  1.4                                       1/99         105.8  729    105.4                                                                               727  0.4                                       HFC-161/propane                                                                44.5/55.5    161.2  1111   161.2                                                                               1111 0.0                                       70/30        156.0  1076   153.2                                                                               1056 1.8                                       90/10        142.2  980    137.9                                                                               951  3.0                                       99/1         131.6  907    130.9                                                                               903  0.5                                       20/80        156.0  1076   153.2                                                                               1056 1.8                                       1/99         139.3  960    138.5                                                                               955  0.6                                       HFC-161/cyclopropane                                                           63.4/36.6    140.8  971    140.8                                                                               971  0.0                                       80/20        138.9  958    138.4                                                                               954  0.4                                       99/1         130.8  902    130.7                                                                               901  0.1                                       30/70        134.2  925    129.8                                                                               895  3.3                                       15/85        125.2  863    116.3                                                                               802  7.1                                       10/90        120.4  830    111.6                                                                               769  7.3                                       1/99         107.1  738    105.5                                                                               727  1.5                                       HFC-227ca/butane                                                               84.4/15.6    77.5   534    77.5 534  0.0                                       92/8         76.4   527    74.3 514  2.5                                       99/1         67.3   464    64.8 447  3.7                                       60/40        75.4   520    67.8 467  10.1                                      61/39        75.5   521    69.0 476  8.6                                       HFC-227ca/cyclopropane                                                         55.8/44.2    126.5  872    126.5                                                                               872  0.0                                       80/20        121.4  837    112.6                                                                               776  7.2                                       85/15        117.0  807    102.1                                                                               704  12.7                                      83/17        119.1  821    106.8                                                                               736  10.3                                      82/18        119.9  827    108.9                                                                               751  9.2                                       30/70        124.8  860    116.5                                                                               803  6.7                                       25/75        123.9  854    110.4                                                                               761  10.9                                      26/74        124.1  856    111.5                                                                               769  10.2                                      27/73        124.3  857    112.7                                                                               777  9.3                                       HFC-227ca/DME                                                                  75.6/24.4    101.0  696    101.0                                                                               6%   0.0                                       90/10        98.1   676    94.3 650  3.9                                       92/8         96.9   668    90.0 621  7.1                                       93/7         96.1   663    86.1 594  10.4                                      40/60        95.1   656    92.7 639  2.5                                       20/80        90.3   623    88.5 610  2.1                                       1/99         85.9   592    85.8 592  0.1                                       HFC-227ca/isobutane                                                            76.8/23.2    90.0   621    90.0 621  0.0                                       90/10        87.5   603    81.8 564  6.5                                       95/5         82.0   565    70.6 487  13.9                                      93/7         85.0   586    75.3 519  11.4                                      92/8         86.0   593    77.6 535  9.8                                       50/50        88.0   607    75.2 518  14.5                                      55/45        88.6   611    83.0 572  6.3                                       53/47        88.4   610    80.5 555  8.9                                       52/48        88.3   609    79.0 545  10.5                                      HFC-227ca/propane                                                              51.6/48.4    159.8  1102   159.8                                                                               1102 0.0                                       30/70        157.9  1089   152.1                                                                               1049 3.7                                       20/80        155.0  1069   143.8                                                                               991  7.2                                       15/85        152.6  1052   140.9                                                                               971  7.7                                       10/90        149.3  1029   139.2                                                                               960  6.8                                       1/99         139.4  961    137.9                                                                               951  1.1                                       80/20        153.6  1059   136.8                                                                               943  10.9                                      78/22        154.9  1068   142.2                                                                               980  8.2                                       79/21        154.3  1064   139.7                                                                               963  9.5                                       HFC-227ea/butane                                                               85.8/14.2    76.8   530    76.8 530  0.0                                       92/8         76.0   524    75.1 518  1.2                                       99/1         69.0   476    67.7 467  1.9                                       60/40        73.8   509    66.1 456  10.4                                      61/39        74.0   510    67.2 463  9.2                                       HFC-227ea/cyclopropane                                                         55.2/44.8    125.1  863    125.1                                                                               863  0.0                                       80/20        119.7  825    111.8                                                                               771  6.6                                       90/10        107.4  741    89.5 617  16.7                                      85/15        115.2  794    102.3                                                                               705  11.2                                      83/17        117.3  809    106.5                                                                               734  9.2                                       84/16        116.3  802    104.5                                                                               721  10.1                                      30/70        123.3  850    116.7                                                                               805  5.4                                       25/75        122.4  844    111.5                                                                               769  8.9                                       23/77        122.0  841    109.7                                                                               756  10.1                                      24/76        122.2  843    110.6                                                                               763  9.5                                       HFC-227ea/isobutane                                                            77.6/22.4    88.8   612    88.8 612  0.0                                       85/15        88.2   608    87.1 601  1.2                                       99/1         71.0   490    67.6 466  4.8                                       50/50        86.3   595    74.9 516  13.2                                      55/45        87.0   600    81.5 562  6.3                                       53/47        86.8   598    79.4 547  8.5                                       52/48        86.6   597    78.1 538  9.8                                       HFC-227ea/propane                                                              50.4/49.6    157.4  1085   157.4                                                                               1085 0.0                                       70/30        155.2  1070   150.8                                                                               1040 2.8                                       90/10        133.7  922    91.5 631  31.6                                      80/20        150.0  1034   133.6                                                                               921  10.9                                      79/21        150.8  1040   136.3                                                                               940  9.6                                       30/70        155.7  1074   151.4                                                                               1044 2.8                                       20/80        153.0  1055   144.3                                                                               995  5.7                                       10/90        147.8  1019   139.6                                                                               963  5.5                                       1/99         139.1  959    137.9                                                                               951  0.9                                       ______________________________________                                    

The results of this Example show that these compositions are azeotropic or azeotrope-like because when 50 wt. % of an original composition is removed, the vapor pressure of the remaining composition is within about 10% of the vapor pressure of the orinal composition, at a temperature of 25° C.

EXAMPLE 3 Impact of Vapor Leakage at 0° C.

A leak test is performed on compositions of HFC-32 and cyclopropane, at the temperature of 0° C. The results are summarized below.

    ______________________________________                                                     0 wt %     50 wt %                                                 Refrigerant evaporated evaporated 0% change in                                 Composition psia    kPa    psia  kPa  vapor pressure                           ______________________________________                                         HFC-32/cyclopropane                                                            83.7/16.3   126.6   873    126.6 873  0.0                                      99/1        119.7   825    118.9 820  0.7                                      60/40       122.5   845    116.4 803  5.0                                      53/47       120.2   829    108.5 748  9.7                                      52/48       119.8   826    107.1 738  10.6                                     ______________________________________                                    

EXAMPLE 4 Refrigerant Performance

The following table shows the performance of various refrigerants in an ideal vapor compression cycle. The data are based on the following conditions.

    ______________________________________                                         Evaporator temperature                                                                              48.0° F. (8.9° C.)                          Condenser temperature                                                                               115.0° F. (46.1° C.)                        Liquid subcooled to  120° F. (6.7° C.)                           Return Gas           65° F. (18.3° C.)                           Compressor efficiency is 75%.                                                  ______________________________________                                    

The refrigeration capacity is based on a compressor with a fixed displacement of 3.5 cubic feet per minute and 75% volumetric efficiency. Capacity is intended to mean the change in enthalpy of the refrigerant in the evaporator per pound of refrigerant circulated, i.e. the heat removed by the refrigerant in the evaporator per time. Coefficient of performance (COP) is intended to mean the ratio of the capacity to compressor work. It is a measure of refrigerant energy efficiency.

    __________________________________________________________________________                Evap. Cond.            Capacity                                     Refrig.    Press.                                                                               Press.                                                                               Comp. Dis. BTU/min                                      Comp.      Psia                                                                              kPa                                                                               Psia                                                                              kPa                                                                               Temp. °F.                                                                    °C.                                                                        COP                                                                               kw                                           __________________________________________________________________________     HFC-32/isobutane                                                               1.0/99.0   32 221                                                                               93 641                                                                               135  57 4.91                                                                              148                                                                               2.6                                       93.8/6.2   154                                                                               1062                                                                              409                                                                               2820                                                                              205  96 4.32                                                                              605                                                                               10.7                                      99.0/1.0   155                                                                               1069                                                                              416                                                                               2868                                                                              214  101                                                                               4.33                                                                              623                                                                               11.0                                      HFC-32/butane                                                                  1.0/99.0   22 152                                                                               68 469                                                                               137  58 5.03                                                                              110                                                                               1.9                                       99.0/1.0   154                                                                               1062                                                                              413                                                                               2848                                                                              214  101                                                                               4.34                                                                              621                                                                               10.9                                      HFC-32/propylene                                                               1.0/99.0   110                                                                               758                                                                               276                                                                               1903                                                                              162  72 4.50                                                                              403                                                                               7.1                                       81.0/19.0  163                                                                               1124                                                                              422                                                                               2910                                                                              197  92 4.25                                                                              609                                                                               10.7                                      99.0/1.0   156                                                                               1076                                                                              418                                                                               2882                                                                              215  102                                                                               4.32                                                                              626                                                                               11.0                                      HFC-32/cyclopropane                                                            1/99       68 469                                                                               183                                                                               1262                                                                              175  79 4.89                                                                              299                                                                               5.3                                       85.2/14.8  163                                                                               1124                                                                              425                                                                               2930                                                                              203  95 4.28                                                                              622                                                                               11.0                                      99/1       156                                                                               1076                                                                              419                                                                               2889                                                                              215  102                                                                               4.32                                                                              628                                                                               11.1                                      HFC-125/propylene                                                              1.0/99.0   109                                                                               752                                                                               275                                                                               1896                                                                              161  72 4.49                                                                              400                                                                               7.0                                       79.5/20.5  124                                                                               855                                                                               318                                                                               2193                                                                              149  65 4.12                                                                              413                                                                               7.3                                       99.0/1.0   128                                                                               883                                                                               337                                                                               2324                                                                              144  62 3.84                                                                              401                                                                               7.1                                       HFC-125/cyclopropane                                                           1/99       67 462                                                                               180                                                                               1241                                                                              175  79 4.85                                                                              293                                                                               5.2                                       91.3/8.7   133                                                                               917                                                                               343                                                                               2365                                                                              147  64 3.92                                                                              421                                                                               7.4                                       99/1       129                                                                               889                                                                               340                                                                               2344                                                                              144  62 3.83                                                                              402                                                                               7.1                                       HFC-134/propane                                                                1.0/99.0   90 621                                                                               232                                                                               1586                                                                              150  66 4.52                                                                              336                                                                               5.9                                       52.3/47.7  107                                                                               738                                                                               270                                                                               1862                                                                              148  64 4.37                                                                              375                                                                               6.6                                       99.0/1.0   50 345                                                                               149                                                                               1020                                                                              150  66 5.04                                                                              243                                                                               4.3                                       HFC-134a/cyclopropane                                                          1/99       66 455                                                                               180                                                                               1241                                                                              175  79 4.85                                                                              292                                                                               5.1                                       65.5/34.5  86 593                                                                               229                                                                               1579                                                                              159  71 4.61                                                                              344                                                                               6.1                                       99/1       60 414                                                                               177                                                                               1220                                                                              151  66 4.69                                                                              269                                                                               4.7                                       HFC-143a/DME                                                                   1.0/99.0   52 357                                                                               150                                                                               1034                                                                              168  75 4.91                                                                              243                                                                               4.3                                       90.9/9.1   116                                                                               801                                                                               302                                                                               2084                                                                              183  84 4.29                                                                              429                                                                               7.6                                       99.0/1.0   118                                                                               813                                                                               322                                                                               2221                                                                              194  90 3.93                                                                              422                                                                               7.4                                       HFC-143a/propylene                                                             1.0/99.0   109                                                                               752                                                                               274                                                                               1889                                                                              161  72 4.50                                                                              400                                                                               7.0                                       89.6/10.4  115                                                                               793                                                                               298                                                                               2055                                                                              155  68 4.28                                                                              408                                                                               7.2                                       99.0/1.0   115                                                                               793                                                                               301                                                                               2075                                                                              155  68 4.24                                                                              406                                                                               7.1                                       HFC-152a/propane                                                               1.0/99.0   89 614                                                                               229                                                                               1579                                                                              150  66 4.54                                                                              333                                                                               5.9                                       45.9/54.1  79 545                                                                               211                                                                               1455                                                                              156  69 4.63                                                                              317                                                                               5.6                                       99.0/1.0   52 359                                                                               156                                                                               1076                                                                              168  76 4.82                                                                              248                                                                               4.4                                       HFC-152a/isobutane                                                             1.0/99.0   31 214                                                                               91 627                                                                               135  57 4.78                                                                              139                                                                               2.4                                       75.5/24.5  49 338                                                                               142                                                                               979                                                                               156  69 4.80                                                                              222                                                                               3.9                                       99.0/1.0   52 359                                                                               154                                                                               1062                                                                              167  75 4.81                                                                              245                                                                               4.3                                       HFC-152a/butane                                                                1.0/99.0   21 145                                                                               65 448                                                                               138  59 4.89                                                                              103                                                                               1.8                                       85.0/15.0  45 310                                                                               135                                                                               931                                                                               162  72 4.87                                                                              215                                                                               3.8                                       99.0/1.0   51 352                                                                               153                                                                               1055                                                                              168  76 4.82                                                                              243                                                                               4.3                                       HFC-152a/cyclopropane                                                          1.0/99.0   66 455                                                                               179                                                                               1234                                                                              175  79 4.84                                                                              290                                                                               5.1                                       44.3/55.7  60 414                                                                               169                                                                               1165                                                                              173  78 4.83                                                                              272                                                                               4.8                                       99.0/1.0   52 359                                                                               155                                                                               1069                                                                              168  76 4.82                                                                              246                                                                               4.3                                       HFC-161/propane                                                                1.0/99.0   90 621                                                                               229                                                                               1579                                                                              150  66 4.53                                                                              334                                                                               5.9                                       44.5/55.5  94 648                                                                               244                                                                               1682                                                                              159  71 4.56                                                                              361                                                                               6.4                                       99.0/1.0   83 572                                                                               229                                                                               1579                                                                              175  79 4.69                                                                              356                                                                               6.3                                       HFC-161/cyclopropane                                                           1.0/99.0   66 455                                                                               178                                                                               1227                                                                              174  79 4.87                                                                              289                                                                               5.1                                       63.4/36.6  75 517                                                                               206                                                                               1420                                                                              174  79 4.79                                                                              328                                                                               5.8                                       99.0/1.0   84 579                                                                               230                                                                               1586                                                                              174  79 4.70                                                                              357                                                                               6.3                                       HFC-227ca/butane                                                               1.0/99.0   21 145                                                                               65 448                                                                               137  58 4.89                                                                              103                                                                               1.8                                       84.4/15.6  34 234                                                                               103                                                                               710                                                                               129  54 4.61                                                                              149                                                                               2.6                                       99.0/1.0   38 262                                                                               115                                                                               793                                                                               127  53 4.45                                                                              160                                                                               2.8                                       HFC-227ca/cyclopropane                                                         1.0/99.0   66 455                                                                               177                                                                               1220                                                                              174  79 4.88                                                                              289                                                                               5.1                                       55.8/44.2  76 524                                                                               202                                                                               1393                                                                              154  68 4.65                                                                              303                                                                               5.3                                       99.0/1.0   40 276                                                                               124                                                                               855                                                                               130  54 4.24                                                                              164                                                                               2.9                                       HFC-227ca/DME                                                                  1.0/99.0   52 359                                                                               149                                                                               1027                                                                              167  75 4.90                                                                              242                                                                               4.3                                       75.6/24.4  66 455                                                                               184                                                                               1267                                                                              142  61 4.48                                                                              260                                                                               4.6                                       99.0/1.0   41 283                                                                               122                                                                               841                                                                               128  53 4.49                                                                              170                                                                               3.0                                       HFC-227ca/isobutane                                                            1.0/99.0   31 214                                                                               90 621                                                                               135  57 4.79                                                                              138                                                                               2.4                                       76.8/23.2  36 248                                                                               106                                                                               731                                                                               130  54 4.61                                                                              155                                                                               2.7                                       99.0/1.0   38 262                                                                               115                                                                               793                                                                               127  53 4.45                                                                              160                                                                               2.8                                       HFC-227ca/propane                                                              1.0/99.0   88 607                                                                               226                                                                               1558                                                                              145  63 4.53                                                                              326                                                                               5.7                                       51.6/48.4  76 524                                                                               205                                                                               1413                                                                              141  61 4.46                                                                              288                                                                               5.1                                       99.0/1.0   40 276                                                                               120                                                                               827                                                                               127  53 4.47                                                                              167                                                                               2.9                                       HFC-227ea/butane                                                               1.0/99.0   21 145                                                                               65 448                                                                               137  58 4.90                                                                              103                                                                               1.8                                       85.8/14.2  34 234                                                                               102                                                                               703                                                                               129  54 4.60                                                                              148                                                                               2.6                                       99.0/1.0   37 255                                                                               113                                                                               779                                                                               127  53 4.46                                                                              157                                                                               2.8                                       HFC-227ea/cyclopropane                                                         1.0/99.0   66 455                                                                               179                                                                               1234                                                                              175  79 4.85                                                                              291                                                                               5.1                                       55.2/44.8  75 517                                                                               201                                                                               1386                                                                              154  68 4.61                                                                              300                                                                               5.3                                       99.0/1.0   42 290                                                                               125                                                                               862                                                                               128  53 4.45                                                                              173                                                                               3.0                                       HFC-227ea/isobutane                                                            1.0/99.0   31 214                                                                               89 614                                                                               135  57 4.79                                                                              138                                                                               2.4                                       77.6/22.4  36 248                                                                               105                                                                               724                                                                               130  54 4.60                                                                              153                                                                               2.7                                       99.0/1.0   38 262                                                                               113                                                                               779                                                                               127  53 4.46                                                                              157                                                                               2.8                                       HFC-227ea/propane                                                              1.0/99.0   88 607                                                                               226                                                                               1558                                                                              145  63 4.53                                                                              326                                                                               5.7                                       50.4/49.6  76 524                                                                               204                                                                               1407                                                                              141  61 4.47                                                                              288                                                                               5.1                                       99.0/1.0   39 269                                                                               119                                                                               820                                                                               129  54 4.35                                                                              160                                                                               2.8                                       __________________________________________________________________________

EXAMPLE 5

This Example is directed to measurements of the vapor pressure of the following liquid mixtures of this invention at 25° C.: HFC-32/isobutane; HFC-32/butane; HFC-32/propylene; HFC-125/propylene; HFC-143a/propylene; HFC-152a/propane; HFC-152a/isobutane; HFC-152a/butane; HFC-152a/cyclopropane; HFC-161/propane; HFC-161/cyclopropane; HFC-227ca/butane; HFC-227ca/cyclopropane; HFC-227ca/DME; HFC-227ca/isobutane; HFC-227ca/propane; HFC-227ea/butane; HFC-227ea/cyclopropane; HFC-227ea/isobutane; and HFC-227ea/propane. The vapor pressures for these mixtures are shown in FIGS. 1-3, 5 and 9-24.

The vapor pressure data for the graph in FIG. 1 are obtained as follows. A stainless steel cylinder is evacuated, and a weighed amount of HFC-32 is added to the cylinder. The cylinder is cooled to reduce the vapor pressure of HFC-32, and then a weighed amount of isobutane is added to the cylinder. The cylinder is agitated to mix the HFC-32 and isobutane, and then the cylinder is placed in a constant temperature bath until the temperature comes to equilibrium, at which time the vapor pressure of the HFC-32 and isobutane in the cylinder is measured. This procedure is repeated at the same temperature with different weight percents of the components, and the results are plotted in FIG. 1.

Data are obtained in the same way for the mixtures plotted in FIGS. 2, 3, 5 and 9-24.

The data in FIGS. 1-3, 5 and 9-24 show that at 25° C., there are ranges of compositions that have vapor pressures higher than the vapor pressures of the pure components of the composition at that same temperature.

EXAMPLE 6

This Example is directed to the measurements of the vapor pressure of the following liquid mixtures of this invention: HFC-32/cyclopropane; HFC-125/cyclopropane; HFC-134/propane; and HFC-134a/cyclopropane. The vapor pressures of these mixtures were measured at particular compositions as shown by the asterisks in FIG. 4 and 6-8, and a best fit curve was drawn through the asterisks.

The procedure for measuring the vapor pressures for mixtures of HFC-32 and cyclopropane was as follows. A stainless steel cylinder was evacuated, and a weighed amount of HFC-32 was added to the cylinder. The cylinder was cooled to reduce the vapor pressure of HFC-32, and then a weighed amount of cyclopropane was added to the cylinder. The cylinder was agitated to mix the HFC-32 and cyclopropane, and then the cylinder was placed in a constant temperature bath until the temperature came to equilibrium at 0° C., at which time the vapor pressure of the content of the cylinder was measured. This procedure was repeated for various mixtures of HFC-32 and cyclopropane as indicated in FIG. 4.

The data in FIG. 4 show that at 0° C., there are ranges of compositions that have vapor pressures higher than the vapor pressures of the pure components of the composition at that same temperature.

The procedure for measuring the vapor pressure of mixtures of HFC-32/cyclopropane was carried out in the same way for mixtures of HFC-125/cyclopropane, HFC-134/propane and HFC-134a/cyclopropane, except that the measurements of the vapor pressure of mixtures of HFC-134/propane were taken at 15° C. and the measurements of the vapor pressure of mixtures of HFC-134a/cyclopropane were taken at 0.01° C.

ADDITIONAL COMPOUNDS

Other components, such as aliphatic hydrocarbons having a boiling point of -60° to +60° C., hydrofluorocarbonalkanes having a boiling point of -60° to +60° C., hydrofluoropropanes having a boiling point of between -60° to +60° C., hydrocarbon ethers having a boiling point between -60° to +60° C., hydrochlorofluorocarbons having a boiling point between -60° to +60° C., hydrofluorocarbon having a boiling point of -60° to +60° C., hydrochlorocarbons having a boiling point between -60° to +60° C., chlorocarbons and perfluorinated compounds, can be added to the azeotropic or azeotrope-like compositions described above.

Additives such as lubricants, surfactants, corrosion inhibitors, stabilizers, dyes and other appropriate materials may be added to the novel compositions of the invention for a variety of purposes provides they do not have an adverse influence on the composition for its intended application. Preferred lubricants include esters having a molecular weight greater than 250. 

We claim:
 1. A maximum pressure azeotropic or azeotrope-like composition consisting essentially of 65-99 weight percent difluoromethane and 1-35 weight percent butane having a vapor pressure ranging from about 229.1 to about 246.8 psia when the temperature has been adjusted to about 25° C.
 2. The maximum pressure azeotropic or azeotrope-like composition of claim 1, said composition consisting essentially of 70-99 weight percent difluoromethane and 1-30 weight percent butane.
 3. A process for producing refrigeration, comprising condensing a composition of claim 1 and thereafter evaporating said composition in the vicinity of the body to be cooled.
 4. A process for producing refrigeration, comprising condensing a composition of claim 2 and thereafter evaporating said composition in the vicinity of the body to be cooled.
 5. A process for producing heat comprising condensing a composition of claim 2 in the vicinity of a body to be heated, and thereafter evaporating said composition. 